1. Field of the Invention
The present invention relates to offshore drilling equipment. More particularly, the present invention relates to improvements in a device of the type illustrated in U.S. Pat. No. 4,410,425, issued to the present applicant for filtering the drilling fluid and cuttings that are brought to the wellhead to be recirculated through a flow line.
2. General Background
During the drilling process and the production of offshore oil and gas wells, cuttings and other debris resulting from the action of the drill bit within the drill hole are brought up to the surface by means of pumping drilling fluid or mud under pressure down the drill pipe into the drill hole and circulating the fluid along with the cuttings and other materials back to the surface through the exterior casing. Upon reaching the surface of the drilled hole, the mud, cuttings and other material are routed up the well casing through the wellhead into a flow line which angularly allows the mud and cuttings to flow away from the drill site to separators where the cuttings are separated from the drilling mud for recirculation of the drilling mud under pressure back down into the well hole for reuse.
One of the most troublesome problems confronted in this operation is the constant coagulation and accumulation of mud and cuttings within the flow line resulting in ultimate blockage of the flow of drilling mud and cuttings therethrough. When the flow line becomes blocked, the flow of drilling mud through the flow line is interrupted. This results in the mud and cuttings being forced up to the surface on the drill floor rather than through the flow line. This causes the loss of drilling mud or fluid which is expensive and time consuming to replace as well as creating an untidy and unsafe work area at the wellhead due to the presence of drilling fluid and cuttings. The time required for unclogging of the flow lines creates rig down time and loss of valuable revenues.
Several apparatuses have been patented which attempt to serve as a filter for the cuttings from a well. They are as follows:
U.S. Pat. No. 3,880,762, issued to Roger Wise, entitled "Separator For Cuttings" teaches a separator for drill bit cuttings being disposed on the top of a well pipe having a container surrounding the pipe in a slide area on the top of the container. The slide area is comprised of a plurality of spaced, elongated elements inclined downwardly from the top of the pipe sleeve. This particular patent addresses the problem of filtering out cuttings which may collect and clog the shaker screen. This particular apparatus would, in effect, require a filter screen which would filter cuttings of a very minute size to prevent clogging of the shale shaker screen and for the purposes of the present invention would be ineffectual and inoperative.
U.S. Pat. No. 4,116,288, issued to William W. Love, entitled "Method And Apparatus For Continuously Separating Lost Circulating Material From Drilling Fluid" teaches the use of a method and apparatus for processing drilling mud. The lost circulating material is retained on a coarse screen while the mud and drilling solids pass through a finer mesh screen. This particular apparatus is a rather involved separator apparatus and would not suit the particular needs of the present invention.
U.S. Pat. No. 4,410,425, issued to the present applicant, discloses a filter apparatus effective for filtering cuttings from drilling fluid as is the purpose of the present invention but is presented with the problems of a primary filter which is not adjustable, a drilling fluid collection area which is not completely efficient during periods of increased flow of drilling fluid, the lack of a means for collecting and guiding cuttings filtered out away from the work site and the lack of a means for easily cleaning cuttings and drilling fluid which may accumulate in the filter and collection tank.
Other patents which are presently in the art are U.S. Pat. No. 3,774,702, issued to Wayland Ellenburg entitled "Formation Chip Sampling Method", U.S. Pat. No. 2,169,675, issued to G. S. Bays, entitled "Back Pressure Control In Pressure Drilling", U.S. Pat. No. 2,514,585, issued to M. L. Natland, entitled "Method For Drilling Wells" and U.S. Pat. No. 2,870,990, issued to T. G. Bergey, entitled "Drilling Fluid Method" are all directed toward cleaning drilling mud and recirculation thereof, but each of these particular apparatuses do not meet the needs of the present invention.